[EE] Switch to Rails 5

See merge request gitlab-org/gitlab-ee!7222

CE upstream - 2018-11-14 13:21 UTC

Closes charts/gitlab#897

See merge request gitlab-org/gitlab-ee!8447

In Rails 5 all models by default inherit from ApplicationRecord.

We want to run CI with rails 4 for a short-term (until we are sure that
we will ship with rails 5). The problem is that rails 4 can not handle
rails 5 schema.rb properly - specifically `t.index` directive can not
handle multiple indexes on the same column.

Because combination of rails 4 + rails 5 schema will be used
only in CI for a short-term, we can just ignore these incompatibility
failures. This patch adds `rails5` helper for specs.

* add_index replaced with t.index
* intiger(size 8) replaced with bigin

* similar to rails 5 it assures that index length is set for blob
  columns also in rails 4
* it also ignores multiple definitions of indexes for mysql, for some
  tables we define multiple indexes on the same set of columns, but with
  different parameters (opclasses, where), these are not supported by
  mysql adapter so the second definition of index is skipped

CI jobs will be triggered both with rails 4 and 5
to make sure we keep backward compatibility if it turns out
we have to switch back to rails 4.

Rails 4 jobs are not allowed to fail for now, these jobs will be
removed in a follow-up MR next cycle.

* updates Gemfile
* uses Rails 5 unless explicitly disable

CE upstream - 2018-11-14 11:23 UTC

See merge request gitlab-org/gitlab-ee!8445

Move cloud-native-image to the post-test stage

Closes charts/gitlab#897

See merge request gitlab-org/gitlab-ce!22942

Bump GitLab Workhorse to 7.1.1

See merge request gitlab-org/gitlab-ce!23053

Bump `binding_of_caller` gem version to 0.8.0

See merge request gitlab-org/gitlab-ce!23040

removed gcp_clusters table and keys

Merge branch '54002-activity-feed-missing-padding-in-event-note-when-a-branch-is-deleted' into 'master'

Resolve "Activity Feed - Missing padding in event note when a branch is deleted"

Closes #54002

See merge request gitlab-org/gitlab-ce!23038

This version now supports redis[s]:// URL schemes.

Resolve "Empty label menu if not logged in"

Closes #53816

See merge request gitlab-org/gitlab-ce!23042

# Conflicts:
#	db/schema.rb

[ci skip]

Revert "Merge branch 'revert-drop-gcp-clusters-table' into 'master'"

See merge request gitlab-org/gitlab-ce!23020

Avoid returning deployment metrics url to MR widget when the deployment is not successful

Closes #53870

See merge request gitlab-org/gitlab-ce!23010

Track Kubernetes errors using Sentry

Closes #53922

See merge request gitlab-org/gitlab-ce!23026

Merge branch '8340-use-iid-instead-of-id-when-displaying-link-to-issue-on-group-security-dashboard' into 'master'

Resolve "Use iid instead of id when displaying link to issue on Group Security Dashboard"

Closes #8340

See merge request gitlab-org/gitlab-ee!8357

CE upstream - 2018-11-14 09:21 UTC

See merge request gitlab-org/gitlab-ee!8441

Update comment in Auto-DevOps.gitlab-ci.yml

See merge request gitlab-org/gitlab-ce!23013

Adds documentation of git trace when git push/pull times out

See merge request gitlab-org/gitlab-ce!23016